Reflecting sunlight with pollutants will not save the planet
In the midst of rising annual temperatures, it is difficult to imagine freezing weather in Chennai. Incredibly, there are reports that the mercury plummeted across much of the Indian subcontinent (including Chennai) in 1815 (though to what extent is debatable). The cause of that dip over two centuries ago is now being investigated as a solution to the climate crisis.
In 1815, Mount Tambora erupted in Indonesia. This was the largest volcanic eruption in human history. Around 100,000 died in the immediate aftermath. Global weather patterns were disrupted. The following year was known as “The Year Without a Summer” because of the drop in temperatures globally.
Incidentally, Mary Godwin conceived of Frankenstein that year while she was stuck near Lake Geneva due to bad weather (as part of a ghost-story writing game with Lord Byron and Percy Shelley).
More recently, in 1991, Mount Pinatubo in the Philippines gave scientists a chance to examine the fallout on weather. Scientists who measured the effects of the eruption calculated that the Earth was half a degree Centigrade cooler for the next 15 months.
These volcanic eruptions have given credence one of the main ideas behind “solar geoengineering”. Solar geoengineering is a broad term used to refer to emergency measures to lower temperatures on earth by reflecting sunlight back into space. It sounds like science fiction, except it is very real and it and it could have major consequences.
Solar geoengineering measures that have been floated include launching gigantic mirrors into space. A more realistic measure is marine cloud brightening which involves injecting chemicals from ships to low-lying clouds to enhance their sunlight reflecting ability. The effects of these measures are, however, regional and temporary.
Scientists have been debating another method as well. Injection of large amounts of sulphate aerosols into a part of the atmosphere known as the stratosphere has been proposed. We know this might lower temperatures from studying volcanic eruptions. Up in the stratosphere, sulphate aerosols reflect sunlight causing cooling below. Scientists have calculated that a 1-degree drop in temperature might be possible by releasing aerosols from airplanes for as little as a few hundred million dollars annually. This is much cheaper than decarbonising the economy.
Solar geoengineering by releasing reflective sulphate aerosols offers the promise of a cheap, and effective solution to the climate crisis, but beneath the surface it is not a true solution. The effects of solar geoengineering are temporary.
Aerosolised sulphates fall out of the stratosphere over a few years and they leave greenhouse gases in the air.
Solar geoengineering does not solve the problem created by emissions or ocean acidification. Since the measures are temporary and the underlying causes remain, ceasing to pump sulphate aerosols might have even more pronounced climate effects. No one knows how long we would have to pump pollutants into the stratosphere, and breaks due to global war or disagreements could be catastrophic.
In addition, we simply do not know what global or local effects might result from solar geoengineering using sulphate aerosols. Small-scale experiments and computer modelling have been proposed but they may not capture the full range of effects — from drought to catastrophic monsoon failure to ozone-layer damage. The tint of the sky might change from blue to white. Blocking out sunlight might also reduce photosynthesis everywhere, disrupting agriculture and ecosystems.
Modern history is replete with examples of how meddling with the environment has led to unpredictable outcomes. Chlorofluorocarbons were considered harmless but their use led to the hole in the ozone layer above Antarctica. Timely detection and a ban on the use of these chemicals averted a bigger catastrophe.
Finally, there are moral and behavioural concerns with releasing sulphate aerosols from airplanes. Who decides when to use it? Some parts of the world might end up with more favourable temperatures than others. In such a scenario, it is easy to imagine a dystopian climate arms race with one country trying to cool the environment with sulphate aerosols and another trying to increase temperature by increasing their greenhouse gas emissions.
The only true solution to the climate crisis is to decarbonise the global economy. If we put off addressing the problem because we think we have other options, we raise a moral hazard. We may feel we have insurance to push the problem into the future, but the truth is we are at a tipping point now. The irony of trying to change the climate by releasing large volumes of pollutants into the atmosphere is that we would be doing what precipitated the climate crisis in the first place.
The longer we wait, the more the Earth will warm. And as this happens, the scenarios that are forecast are bleak — rising sea levels, severe weather, prolonged droughts, and famines. But as we head towards the doomsday scenario, countries may also be willing to gamble on untested ideas.
Research on solar geoengineering might be necessary in the future, but it should be considered only after other options have been exhausted. Ultimately, I agree with Erle Ellis in Anthropocene that “solar geoengineering using stratospheric sulphates is a shining example of solving one problem by creating an even bigger one.”
Anirban Mahapatra, a microbiologist by training, is the author of COVID-19: Separating Fact From Fiction
These are his personal views